Omtrek ↔ Diameter Calculator
Use this tool to calculate a circle’s diameter from its omtrek (circumference), or the omtrek from a known diameter.
Tip: commas and periods are both accepted as decimal separators.
What is an omtrek diameter calculator?
An omtrek diameter calculator helps you convert between two core circle measurements: the omtrek (circumference) and the diameter. This is useful for school math, engineering sketches, woodworking, design, cycling, and any practical task where circular objects are measured.
If you know one value, you can calculate the other instantly using the number π (pi). This page gives you a fast calculator plus a clear explanation of the formulas.
Key formulas
1) From diameter to omtrek
Use this when the diameter is known:
- C = π × d
- C = circumference (omtrek)
- d = diameter
- π ≈ 3.14159265
2) From omtrek to diameter
Use this when the circumference is known:
- d = C / π
How to use the calculator
- Select the calculation direction (Omtrek → Diameter or Diameter → Omtrek).
- Enter your number.
- Choose your unit (mm, cm, m, in, or ft).
- Click Calculate to see the result, radius, and area.
Worked examples
Example A: Omtrek to diameter
Suppose the omtrek is 62.8 cm.
- d = 62.8 / π ≈ 19.99 cm
- Rounded, the diameter is about 20 cm
Example B: Diameter to omtrek
Suppose the diameter is 15 cm.
- C = π × 15 ≈ 47.12 cm
Common mistakes to avoid
- Mixing radius and diameter (diameter = 2 × radius).
- Forgetting to keep units consistent.
- Rounding too early in multi-step calculations.
- Using 3.14 for π in precision-critical work (use more decimals).
FAQ
Is omtrek the same as circumference?
Yes. “Omtrek” is Dutch for circumference.
Can I use inches or feet?
Yes. The calculator keeps input and output in the same chosen unit.
Does this work for all circles?
Yes, as long as the shape is a true circle and your measurement is accurate.
Final note
Whether you need a quick school answer or a practical workshop measurement, this omtrek diameter calculator gives a fast and reliable conversion. For best accuracy, measure carefully and round only at the final step.